1. Field of the Invention
The present invention relates generally to a resonance circuit using a variable capacitance semiconductor element, and is directed more particularly to a resonant circuit using a variable capacitance diode.
2. Description of the Prior Art
Recently, a so-called electronic tuner (which will be hereinafter referred to as an ET tuner) using a variable capacitance semiconductor element (which will be hereinafter referred to as a varicap) has been proposed. However, the non-linearity of the varicap may cause a tuning frequency deviation (which may be a cause of tracking error) due to the large amplitude operation of the local oscillator in a television tuner. Also, mutual modulcation, cross modulation and so on in an FM tuner may result, and for these reasons ET tuners are not used widely at present.